1. Field of the Invention
This invention relates to a process for removing slag from and about the surfaces of a combustion chamber of a burner of the type used in industrial, electric arc furnaces, wherein the combustion chamber of the burner is exposed to the work product and the metallic and nonmetallic particles in the furnace environment results in an accumulation of slag on the burner surfaces. More specifically, the invention relates to a method of adjusting the supply of fuel and oxygen to the flame from an open combustion chamber burner of an electric arc furnace or the like so as to first heat the slag accumulated on the burner to a very hot condition and then supply an excess of oxygen through the combustion chamber of the burner to cause the slag to oxidize and therefore dissipate.
2. Description of the Prior Art
When solid metals are being heated in an electric arc furnace or similar chamber so as to melt the solid products into a molten state, it is normal that small particles of molten metal are continuously dispersed throughout the furnace environment. This is caused by the action of the arcs from the electrodes to the metal to be melted and from the interaction of the oxygen and the molten metal during the refining of the metal. This splashing of the molten metal within the furnace chamber usually results in some of the metal making contact with the the burner and the furnace wall, both of which are cooler than the molten metal, resulting in some of the particles solidifying on the surfaces of the burner and wall. If the burner has its combustion chamber extendinq toward the work product, it is likely that some of the molten metal from the work product will splash into and accumulate on and around the combustion chamber of the burner.
Most burners are operated at a surface temperature which is lower than the temperature required to melt steel or other work products. Some burners are internally cooled by the circulation of water in contact with the burner about the combustion chamber, so that the surface of the combustion chamber is maintained at a reduced temperature. Also, fuel film cooling of the surfaces of the burner combustion chamber results in the lowering of the temperature of the burner. For example, U.S. Pat. No. 4,473,350 discloses a burner having a combustion chamber that is open to the furnace atmosphere, but the burner is cooled by the circulation of a cooling liquid about the combustion chamber, and by a film of fuel formed adjacent the surfaces of the combustion chamber. As a result, when molten metal splashes into the combustion chamber, there is some likelihood that the molten metal will accumulate on the combustion chamber as slag. This is particularly so when a burner is idling, with only a minimum amount of oxygen and fuel being supplied to the burner to create a very small pilot flame in the combustion chamber of the burner.
Most hiqh velocity burners are mounted in the sidewalls of a furnace, and the build-up of slag on the burner can eventually clog the gas entry holes and other passageways of a burner. Also, the accumulation of slag on the surfaces of the burner makes it more difficult to cool the surfaces of the burner, and the temperature level of the burner tends to rise during normal operation. This tends to cause the burner to deteriorate more rapidly, and the burner must be replaced more frequently.
Preventive maintenance can be conducted with respect to burners on a regular basis, by removing a burner from its furnace and then chipping the slag away from the surface of the burner and its nose tip. For example, preventive maintenance can be performed by removing one of the three burners typically used in an electric arc furnace at the end of every eight hour shift. The withdrawn burner is cleaned while a substitute burner is used with the furnace. The burner that has been removed is cleaned bv chipping out the slag, and if necessary, replacing worn components. Typically, this kind of preventive maintenance would require about three hours of maintenance for each twenty four hours of furnace operation.